Most of the commercially available petrochemical products contain mercury and, for example, mercury and metallic material, employed to form tanks mounted on an LPG tanker, form amalgam, which dissolve the metallic material of the tanks into petroleum. Also, it has been well known in the art that a sample composed mainly of hydrocarbons such as, for example, naphtha, contain mercury, particularly dimethylmercury. It is also well known that various components of mercury are responsible for the degradation of the capacity of a catalyst such as paradigm or platinum employed for producing various kinds of petrochemical products from naphtha. For this reason, countermeasures have been considered necessary to measure the amount of mercury contained in the sample composed mainly of hydrocarbon and to remove the mercury when the amount of mercury contained in the sample composed mainly of the hydrocarbon exceeds a predetermined value.
Hitherto, attempts for mercury measurement have been made to use a heat-vaporization analyzing apparatus including a sample boat in which a sample composed mainly of hydrocarbon is directly injected. With this heat-vaporization analyzing apparatus, mercury contained in the sample is measured after having been vaporized by heating the sample boat within a combustion tube. Also, during the measurement, additives are added together with the sample to remove interfering gases that are generated from the sample and are likely to disturb the mercury measurement.
However, with the conventional method of measuring mercury discussed above, it has been experienced that when mercury contained in the sample is vaporized by heating, hydrocarbon is simultaneously volatized from the sample to produce an inflammable gas. Accordingly, in order to avoid a rapid generation of the inflammable gas, stringent measurement conditions are required as to the quantity, type and flow rate of the sample and also as to the temperature rise rate of the sample and so on. Also, similarly stringent requirements are imposed on selection of the additives.
In view of the foregoing, the method of measuring mercury and the apparatus therefor have been suggested, in which the severe measuring conditions are alleviated to facilitate measurement of mercury with no difficulty. (See the Patent Document 1 listed below.) According to this mercury measuring method, in a condition while a gas containing no mercury flows through a column, hydrocarbon is injected into the column to allow mercury, contained in a sample composed mainly of hydrocarbon, to be adsorbed by an adsorbent contained within the column. On the other hand, components such as, for example, hydrocarbon left when the mercury is removed by adsorption are discharged to the outside together with the gas and then removed from the column. The column is subsequently inserted in a mercury measuring apparatus, in which the mercury adsorbed by the adsorbent, is heated to vaporize for measurement. At the time of measurement, since even when the mercury is heated to vaporize, hydrocarbon has already been removed from the column, no inflammable gas is generated. Also, since only the gas flowing through the column, but containing no mercury and the mercury adsorbed by the adsorbent remain within the column and the gas, which would undesirably interfere the mercury measurement, does not exist within the column, no addition of additives is required to remove the interfering gas. For this reason, there is no need to set up the severe measuring conditions such as those hitherto required and measurement of mercury can be accomplished easily.
[Patent Document 1] JP Laid-open Patent Publication No. 2001-221787